The design of a shoe sole renders it possible to provide a shoe with a plethora of different properties, which may be pronounced to different degrees depending on the kind of shoe. Primarily, shoe soles serve protective functions. They protect the foot from injury by their increased hardness compared to the shoe shaft, for example caused by pointed objects on which the wearer may tread. Furthermore, the shoe sole usually protects the shoe from excessive wear by an increased abrasion resistance. Shoe soles may also increase the grip of a shoe on the respective ground. Further functions of a shoe sole may be to provide a certain stability to the course of movements. In addition, a shoe sole may provide a damping action to cushion the forces occurring during contact of the shoe with the ground. Finally, a shoe sole may also protect the foot from dirt or spray water or provide a plurality of further functionalities.
To meet this plurality of requirements, which arise from the above mentioned exemplary functions, many different materials for the manufacture of shoe soles are known from the prior art. As examples for these different materials, ethylene-vinyl-acetate (EVA), thermoplastic polyurethane (TPU), rubber, polypropylene (PP) or polystyrene (PS) shall be mentioned here. Furthermore, the use of expanded materials, in particular expanded thermoplastic polyurethane (eTPU) or expanded polyether-block-amide (ePEBA), were considered for the manufacture of a shoe sole. Expanded TPU and expanded PEBA distinguish themselves by a low weight and good elasticity- and damping properties.
For example, the WO 2005/066250 A1 describes a sole made from expanded thermoplastic polyurethane, which may be connected with a shoe shaft without an additional bonding agent. The DE 10 2012 206 094 A1 and EP 2 649 896 A2 disclose shoes with soles with particles made from eTPU and methods for their manufacture.
To selectively influence the properties of the sole, the use of additional functional elements, as for example a reinforcing element or a support element, is known from the prior art. Such a reinforcing- or support element can increase the stability of the sole in chosen regions, like, for example, the medial region of the midfoot, and can serve to relief the musculoskeletal system, for example during running on uneven terrain or when over-pronating.
A disadvantage of the reinforcing- and support elements known from the prior art is, however, that they are typically integrally molded or formed from a single base material. Hence, the flexibility- and deformation properties of the reinforcing element are already determined throughout the entire reinforcing element to large degrees by the selection of the base material. Also, the number of possible functions that can be assumed by such a reinforcing element is limited.
It is therefore a problem underlying the present invention to provide support elements for soles of shoes and methods for their manufacture that further increase the possibilities to influence the properties of a sole. Herein, the manufacture shall involve as small a number of individual manufacturing steps as possible and as little manufacturing expenses as possible.